How does the HDFS Client knows the block size while writing

Question

HDFS Client is outside the HDFS Cluster. 

How DOES the HDFS Client know the Blocksize? Block size is configured in the Name node and the HDFS Client has no idea about the block size then how it will split the file into blocks?

Answer 1

HDFS is designed in a way where the block size for a particular file is part of the MetaData.

The client can tell the NameNode that it will put data to HDFS with a particular block size. The client has its own hdfs-site.xml that can contain this value, and can specify it on a per-request basis as well using the -Ddfs.blocksize parameter.